1. Field of the Invention
This invention relates to an improved catalyst useful in a process of preparing aromatic compounds by contacting a feed consisting essentially of C.sub.2 -C.sub.10 paraffins or olefins with a crystalline aluminosilicate zeolite having a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of at least about 12 and a constraint index of from 1 to about 12. In particular, the invention is concerned with such zinc-containing zeolites to which another metal has been added to prevent elution of the zinc at high temperatures.
2. Discussion of the Prior Art
It is known to contact various hydrocarbon fractions with acidic catalysts such as solid siliceous acidic catalysts, including crystalline aluminosilicate zeolites. These catalysts have been used in a wide variety of reactions including cracking, isomerization, aromatization and the like. Representative United States patents concerning contacting various hydrocarbon fractions with zeolites are U.S. Pat. Nos. 3,140,249, 3,140,251, 3,140,253 and 3,140,322.
The formation of aromatic compounds from low molecular weight hydrocarbons, including paraffins, olefins and mixtures thereof, is known in the art, as taught, for example in U.S. Pat. Nos. 3,296,324 and 3,374,281.
It is also known, for example from U.S. Pat. No. 3,331,767, that in certain reactions involving 5A pore size zeolites (erionite for example) such as hydrocracking, one of the disclosed forms of the zeolite is the zinc-containing zeolite that has been combined with another metal such as platinum, nickel or cobalt.
U.S. Pat. No. 3,700,585 teaches that the original cation of a zeolite may be replaced with, for example, zinc or with a hydrogenation component such as nickel. However, the reference does not suggest a zeolite containing both of these. The disclosure of U.S. Pat. No. 3,702,886 is similar, but neither does it disclose a zeolite containing zinc and another metal.